This invention relates to medical retrieval devices for entrapping or removing objects from a body, particularly calculi from the urinary and biliary systems.
Medical instruments are currently in use that reduce the invasiveness and potential trauma previously associated with various medical procedures. One such procedure is the removal of objects, such as kidney stones and gallstones, from the body. Various medical retrieval devices are available which allow objects to be removed from the body without requiring major surgery. Typically, such instruments consist of 2 or more flexible elements that are joined at their proximal ends and may or may not be joined at their distal ends. The flexible elements, such as wires, are formed in the shape of a resiliently collapsible basket, cage, grasper, or other entrapping configuration. This basket is attached to a drive wire or actuation cable that passes through the lumen of a small diameter (typically 1 mm (3.0 Fr) or less) flexible sheath, which is usually greater than 50 cm in length. The sheath and drive wire comprise the shaft portion of the device. At the proximal end of the shaft, the sheath and drive wire are attached to a multi-part handle, normally constructed of thermoplastic materials, which can typically be operated by the user with a single hand. By manipulating the handle, the drive wire can be pulled back relative to the sheath, collapsing the basket as it retracts into the sheath. In this closed position, the sheath can be passed through the working channel of an endoscope to the proximity of the object to be removed within the patient's body. By manipulating the handle, which remains outside the endoscope and the patient's body, the basket is deployed from the end of the sheath, and expands to its open position. The device is then manipulated using the handle until the object becomes enclosed within the basket. This manipulation may include advancing, withdrawing and/or rotating the basket in order to get the object to pass between the flexible elements that comprise the basket. When the object has been successfully engaged within the basket, the basket is partially closed to secure the object within the basket wires, and the endoscope and the retrieval device containing the object are then simultaneously removed from the body.
Many different basket configurations are in use. When the basket wires are joined at their distal ends, this is often accomplished by securing the wires inside a small diameter tube, which typically has a length of 0.1-0.2 inches. However, such a tube has the disadvantage that it can cause trauma to body tissue because of its small diameter (typically 1 millimeter or less). In addition, it can be difficult or impossible with this basket configuration to retrieve objects that are positioned in difficult to reach locations, such as kidney stones located in a calyx of the kidney. Several prior art basket configurations have attempted to overcome these limitations. U.S. Pat. No. 4,590,938 (1986) to Segura et al. and U.S. Pat. No. 6,224,612 (2001) to Bates et al. disclose baskets with unsecured protrusions of the basket wires at the distal tip. These baskets have the disadvantage of protruding tips at the distal end that can make the retrieval of objects that are positioned in difficult to reach locations difficult or impossible. U.S. Pat. No. 5,057,114 (1991) to Wittich et al. and U.S. Pat. No. 5,064,428 (1991) to Cope et al. disclose baskets without extending tips. Wire loops in the basket are secured together at their distal ends using a urethane coated suture. These baskets have the disadvantage of questionable strength and stability. U.S. Pat. No. 5,989,266 (1999) to Foster et al. and U.S. Pat. No. 6,159,220 (2000) to Gobron et al. disclose baskets without extending tips. Intertwined basket wires or interconnecting loops made from the basket wires at the distal end of the basket are used to connect the basket wires together without using a protruding tip. While these baskets overcome the potential trauma and difficult retrieval location limitations caused by a protruding tip, some new limitations are introduced. In these configurations, stability of the basket wires previously provided by the protruding tip is lost. Without means to securely maintain the position of the basket wires relative to one another, stress from the surrounding anatomy or the object may force the basket wires radially out of their unrestricted configuration, possibly rendering the retrieval of the object more difficult or impossible. U.S. Pat. No. 6,527,781 (2003) to Bates et al. discloses a basket with a reversed cap that secures the basket wires at the distal end of the basket but extends proximally, into the center of the basket. This basket has the disadvantage of the cap being within the basket and possibly interfering with the object to be captured. All of the aforementioned patents are incorporated herein by reference. There is a need for an improved medical retrieval basket that does not have a protruding distal tip, but yet has a means for keeping the basket wires stable and securely positioned at the distal end of the basket.
In certain situations when a flexible endoscope is used, it may be necessary to articulate the tip of the endoscope significantly in order to reach the location of the object to be retrieved. This is accomplished using the active deflection mechanism of the endoscope. However, the shaft of the retrieval device, located in the endoscope's working channel, can in some situations limit the deflection of the endoscope. This can frequently be the case in difficult to reach locations, such as the lower poles of the kidney. U.S. Pat. No. 6,325,807 (2001) to Que and U.S. Pat. No. 6,398,791 (2002) to Que et al illustrate retrieval devices with a portion of the sheath near the distal end being more flexible than the rest of the sheath. These patents are incorporated herein by reference.
U.S. Pat. No. 6,190,394 (2001) to Lind et al illustrates a retrieval device with basket wires having differing sizes, cross sectional shapes and/or spacing. This patent is incorporated herein by reference.